PHYSIOLOGY 281 



conditions and in a solution free from nitrates, could make use 

 of certain alkaloids as a source of nitrogen. Of the alkaloids 

 used, this was found to be true for the sulphates and hydro- 

 chlorides of atropine, cocaine and morphine; quinine, although 

 it had no deleterious action, was not assimilated, whilst 

 strychnine showed a marked toxic action. Clautriau * found 

 that alkaloids supplied to the higher plant as the sole source 

 of nitrogen are not utilized. 



With regard to the higher plants, De Vries considers that 

 alkaloids are not essential for the well-being of the plant, 

 since in the germination of the seed of the potato, the thorn- 

 apple (Datura Stramonium) and nux vomica (Strychnos nux 

 vomica), little or no diminution in the substances in question 

 occurs. This opinion is to a certain extent supported by the 

 fact that their presence depends, at any rate in some cases, on 

 the conditions of cultivation ; for instance, quinine does not 

 occur in cinchona cultivated in hot-houses in this country. 



Lotsy f considers that alkaloids, such as quinine, are not 

 decomposition products of proteins, but direct synthetic sub- 

 stances. In the case of Cinchona , he found that the bases oc- 

 cur in parenchyma cells, provided that they do not contain 

 calcium oxalate, either in solution in the cell sap, when the 

 tissue is very young, or in a solid state in older parts. They 

 are first formed in the leaves, and ultimately transferred to 

 the bark. 



On the other hand, caffeine and theobromine, which 

 strictly speaking are purines, are generally considered to be 

 decomposition products of proteins, J they are formed in places 

 of great cellular activity and their disappearance is never ac- 

 companied by a concomitant increase of albuminous sub- 

 stances. 



These particular substances may correspond to urea and 

 uric acid of higher animals, for the purine nucleus is charac- 

 teristic of xanthine bases, such as uric acid ; and derivatives 

 of xanthine, such as guanine and adenine, are found in caf- 

 feine and theobromine. In this connexion one important 

 point of distinction between animals and plants may be men- 



* Clautriau : loc. cit. 



t Lotsy : " Bull. Inst. Bot. Buitenzorg," No. 3, 1900. 



: Clautriau : loc. tit. 



